Process for the production of 3-mono or 3,5 dihalogenated 4-acetoxystyrene, its polymerization, and hydrolysis

ABSTRACT

The present invention relates to a process for the production of 3-mono or 3,5-disubstituted-4-acetoxystyrene wherein the 3- or 3,5-substitution is independently C 1  to C 10  alkyl, chlorine, bromine, iodine, --NO 2 , --NH 2 , or --SO 3  H, a process for its polymerization, hydrolysis, and use in a variety of compositions.

This is a division of copending application Ser. No. 07/312,170, filedon 2/21/89, now U.S. Pat. No. 4,868,257.

BACKGROUND OF THE INVENTION

The present invention relates to a process for the production of 3-monoor 3,5-disubstituted-4-acetoxystyrene wherein the 3- or 3,5-substitutionis independently C₁ to C₁₀ alkyl, chlorine, bromine, iodine, --NO₂,--NH₂, or -SO₃ H; a process for its polymerization, and hydrolysis. Inits most preferred form, the invention relates to 3-mono- and3,5-dihalogenated 4-acetoxystyrenes which contain chlorine or bromine asthe halogen, and a method of preparation thereof.3,5-dibromo-4-hydroxystyrene compounds have been known for a long timeand were initially prepared from 4-hydroxycinnamic acid by

(a) bromination of positions 3 and 5 on the ring as well as addition ofbromine to the double bond,

(b) dehydrobromination with concurrent decarboxylation, leading toreconstitution of the vinylic double bond,

(c) then, addition of hydrogen bromide to said double bond to form asaturated vicinal dibromide,

(d) finally, by debromination for reconstitution of the vinylic doublebond (see Liebigs Annalen der Chemie, 322, 235 (1902)) as shown in thefollowing scheme: ##STR1## The existing process, based on cinammic acidderivatives, does however have considerable disadvantages in terms ofthe preparation method. In particular, the decarboxylation necessary inthis method proves to be disadvantageous. Moreover, out of 7 bromineatoms required in the course of this synthesis, only 2 remain in thefinal product. It was therefore desirable to develop a synthesis makingmore economical use of bromine.

It is known in the art to produce monomers, homopolymers and copolymersof unsubstituted 4-acetoxystyrene and to hydrolyze the same to produce4-hydroxystyrene derivatives or polyvinyl phenols. Such find use in theproduction of photoresists, adhesives, coating compositions and thelike. In particular, polymers or copolymers prepared fromnon-halogenated monomers are used for preparing coating compositions andas binders for photoresists. In this connection, reference is made topost-brominated poly(4-hydroxy)styrenes which are used in accordancewith German patent application P No. 37 30 784.3 as radiation-sensitivecompounds in corresponding photoresists. The monomeric acetoxystyrene ofthis invention finds use as an intermediate in the production of suchpolymers as poly(3-mono or 3,5 dimethyl-4-acetoxystyrene) andpoly(3-mono or 3,5-dimethyl-4-hydroxystyrene). These later compounds areuseful as improved binder resins for photoresists which have a moreadvantageous dissolution rate in commercially accepted photoresistdevelopers, and are more fully described in U.S. patent application Ser.No. 097,815 filed on Sept. 16, 1987 and which is incorporated herein byreference.

Alpha acetoxystyrene and beta acetoxystyrenes are described in U.S. Pat.No. 4,144,063 and acetoxymethylstyrene is taught in U.S. Pat. No.3,963,495. U.S. Pat. No. 4,075,237 describes1,4-dimethyl-2-hydroxystyrene, while U.S. Pat. No. 4,565,846 teaches theuse of poly(3,5-dimethyl-4-hydroxystyrene). Japanese patent No. 84023747describes anti-static compounds employing poly-acetoxymethylstyrene andU.S. Pat. No. 4,221,700 describes a stabilized synthetic polymercomposition using poly(alkylated alkenylphenol) including 2-methylparavinyl phenol. U.S. Pat. Nos. 4,600,683 and 4,543,397 describe poly(alphamethyl vinylphenol). U.S. Pat. Nos. 4,517,028; 4,460,770 and4,539,051 describe dimethyl vinyl phenol. One preferred product of thisinvention is 3,5-dibromo-4-hydroxystyrene which is particularly usefulas a binding resin for o-quinone diazides in the production of x-raysensitive photoresists.

SUMMARY OF THE INVENTION

The invention provides a process for the production of 3-mono or3,5-disubstituted-acetoxystyrene which comprises:

(a) acylating phenol to produce 4-hydroxyacetophenone; and

(b) reacting the 4-hydroxyacetophenone with a reagent under conditionsto form 3-mono or 3,5-disubstituted-4-hydroxyacetophenone; and

(c) esterifying the 3-mono or 3,5-disubstituted-4-hydroxyacetophenone,preferably with acetic anhydride, to form 3-mono or3,5-disubstituted-4-acetoxyacetophenone; and

(d) reducing the 3-mono or 3,5-disubstituted-4-acetoxyacetophenone witha sufficient amount of a reducing agent to produce 1-(3'-mono or3',5'-disubstituted-4,-acetoxyphenyl)ethanol; and

(e) dehydrating the 1-(3'-mono or3',5'-disubstituted-4'-acetoxyphenyl)ethanol to produce 3-mono or3,5-disubstituted-acetoxystyrene; wherein said substitutions areselected from the group consisting of Cl, Br, I, NO₂, NH₂, SO₃ H, or C₁-C₁₀ alkyl. The invention also provides a process.for the production ofpoly(3-mono or 3,5-disubstituted-4-acetoxystyrene) which comprises:

(a) acylating phenol, preferably with acetic anhydride and using HF as acatalyst to produce 4-hydroxyacetophenone; and

(b) reacting the 4-hydroxyacetophenone with a reagent under conditionsto form 3-mono or 3,5-disubstituted-4-hydroxyacetophenone; and

(c) esterifying the 3-mono or 3,5-disubstituted-4-hydroxyacetophenone,preferably with acetic anhydride to form 3-mono or 3,5-disubstituted-4-acetoxyacetophenone; and

(d) reducing the 3-mono or 3,5-disubstituted-4'-acetoxyacetophenone witha sufficient amount of a reducing agent to produce 1-(3,-mono or3',5'-disubstituted-4'-acetoxyphenyl)ethanol; and

(e) dehydrating the 1-(3,-mono or3',5'-disubstituted-4'-acetoxyphenyl)ethanol to produce 3-mono or3,5-disubstituted-acetoxystyrene; and

(f) free radical polymerization of the 3-mono or3,5-disubstituted-4-acetoxystyrene to form poly(3-mono or3,5-disubstituted-4-acetoxystyrene) having a molecular weight in therange of from about 1,000 to about 800,000, preferably about 5,000 toabout 500,000;

wherein said substitutions are selected from the group consisting of Cl,Br, I, NO₂, NH₂, SO₃ H, or C₁ -C₁₀ alkyl. The invention still furtherprovides a process for the production of poly(3-mono or3,5-disubstituted-4-hydroxystyrene) which comprises:

(a) acylating phenol, preferably with acetic anhydride to produce4-hydroxyacetophenone; and

(b) reacting the 4-hydroxyacetophenone with a reagent under conditionsto form 3-mono or 3,5-disubstituted-4-hydroxyacetophenone; and

(c) esterifying the 3-mono or 3,5-disubstituted-4-hydroxyacetophenone,preferably with acetic anhydride to form 3-mono or3,5-disubstituted-4-acetoxyacetophenone; and

(d) reducing the 3-mono or 3,5-disubstituted-4-acetoxyacetophenone witha sufficient amount of a reducing agent to produce 1-(3'-mono or3',5'-disubstituted-4'-acetoxyphenyl)ethanol; and

(e) dehydrating the 1-(3'-mono or3',5'-disubstituted-4'acetoxyphenyl)ethanol to produce 3-mono or3,5-disubstituted-4-acetoxystyrene; and

(f) free radical polymerization of the 3-mono or3,5-disubstituted-4-acetoxystyrene to form poly(3-mono or3,5-disubstituted-4-acetoxystyrene) having a molecular weight in therange of from about 1,000 to about 800,000, preferably about 5,000 toabout 500,000; and

(g) hydrolyzing the poly(3-mono or 3,5-disubstituted-4-acetoxystyrene)to form poly(3-mono or 3,5-disubstituted-4-hydroxystyrene) having amolecular weight in the range of from about 1,000 to about 500,000,preferably about 5,000 to about 500,000;

wherein said substitutions are selected from the group consisting of Cl,Br, I, NO₂, NH₂, SO₃ H, or C₁ -C₁₀ alkyl.

In one more preferred form of the invention there is provided a methodfor preparing 3-mono- and 3,5-dihalogenated 4-hydroxy- and4-acetoxystyrenes, which comprises:

(a) halogenation of a 4-hydroxyacetophenone with general formula##STR2## wherein

R₁ is hydrogen or alkyl, in particular C₁ -C₁₀ alkyl, and

R₂ and R₃ are independently hydrogen, alkyl, alkoxy, or halogen, whereinR₁ and R₂ may also be combined to form a cycloaliphatic ring, consistingin particular of 6 to 12 members; and

(b) esterification (protection) of the hydroxyl function to form ahalogenated 4-acetoxyacetophenone derivative; and

(c) reduction of the ketone function to a hydroxyl function,

(d) dehydration to form 3-mono or 3,5-dihalogenated 4-acetoxystyrene,and where appropriate

(e) hydrolysis of the protective group to form the 3-mono or3,5-dihalogenated 4-hydroxystyrene.

Halogenation is preferable chlorination or bromination, but mostpreferably bromination.

In the preferred embodiment, the compounds with general formula I, havethe following substituents:

R₁ is hydrogen or (C₁ -C₃) alkyl, especially methyl; and

R₂ and R₃ are preferably the same and are hydrogen, (C₁ -C₃) alkyl, (C₁-C₃) alkoxy, or bromine.

Compounds with general formula I which contain hydrogen for R₂ and R₃are particularly preferred. When R₁ is hydrogen, the extent ofhalogenation (i.e. whether a 3-monohalo product or a 3,5-dihalo productis formed) depends on the molar ratio of halogen to the compound withgeneral formula I that is used.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the preferred embodiment, the monomers are 3,5-disubstituted and thepreferred substitution is dibromo. The preferred embodiment will now bedescribed in detail. The other substitutions are obtained analogously.

In the process for the production of 3,5-dibromo-4-acetoxystyrene, onebegins with phenol and acylates it, preferably with acetic anhydride viaa Friedel-Crafts catalysis or Fries rearrangement to produce4-hydroxyacetophenone. This is then reacted with a sufficient amount ofbromine to produce the desired 3- or 3,5-substitution. In the preferredembodiment, the substitution is 3,5-dibromo, therefore the4-hydroxyacetophenone is reacted with two molar equivalents of bromine.This 3,5-dibromo-4-hydroxyacetophenone is then esterified with aceticanhydride to form 3,5-dibromo-4-acetoxyacetophenone. The latter is thenreduced to form 1-(3',5'-dibromo-4'-acetoxyphenyl)ethanol. This is thendehydrated with an acid or base to form 3,5-dibromo-4-acetoxystyrenemonomer. A typical reaction sequence may be described schematically asfollows: ##STR3##

In the preferred embodiment the first reaction steps proceed as follows.That is, one charges the reaction vessel with, a slight excess of aceticanhydride and a Friedel-Crafts catalyst such as hydrogen fluoride. Theacylation is conducted at a temperature of from about 5° C. to about100° C., or more preferably from about 20° C. to about 80° C. A mostpreferred temperature is about 50° C. The reaction proceeds at apreferred pressure of from about 700 mm Hg to about 780 mm Hg for fromabout 1 to about 5 hours. Although hydrogen fluoride is the preferredcatalyst, other Lewis acids may be also used such as AlCl₃, BF₃, HClO₄,FeCl₃ and SnCl₄. In the alternative, the acylation may be conducted by aFries rearrangement, in a manner well known to the skilled artisan. Thereaction product 4-hydroxyacetophenone is then reacted with a sufficientamount of a reagent to produce the desired 3- or 3,5- substitution.Although bromine is used in the preferred embodiment, in order to obtainthe other substituents of this invention, the other preferred reactantsnon-exclusively include chlorine, iodine, nitric acid, sulfuric acid andC₁ to C₁₀ alkyl halides.

Attempts to directly reduce the keto functionality in 3,5-dibrominated4-hydroxyacetophenone by means of e.g. catalytic the hydrogenation orcomplex hydrides, as known to the skilled artisan, invariably lead tooverreduction with exclusive formation of 3,5-dibromo-4-ethylphenol.

While not wishing to be bound by theory it is believed that thisbehavior is caused by formation of quinonemethide intermediates whichare then preferentially reduced at the methide carbon as shown in thefollowing scheme: ##STR4##

This undesirable behavior can be pre-empted by obviating phenolate ionformation, which is essential to the above mechanism. This is mosteasily prevented by protecting the phenolic functionality, e.g. byesterification.

Esterification of the hydroxyl group for its protection is preferablyaccomplished with acetyl chloride or with acetic anhydride. However, anyreagents known to protect hydroxyl functions can be used. These includein particular the formation of ethers, such as methyl, methoxymethyl,2-methoxyethoxymethyl, methylchiomethyl, tetra-hydropyranyl,cyclopropylmethyl, allyl, isopropyl, cyclohexyl, t-butyl, benzyl,o-nitrobenzyl, 9-anthrylmethyl, and 4-picolyl ethers, but also silylethers, such as trimethylsilyl and t-butyldimethylsilyl ethers, esterssuch as acetates, pivaloates, benzoates, and 9-fluorene-carboxylates,carbonates such as methyl, 2,2,2-trichloroethyl, vinyl, and benzylcarbonates, arylcarbamates, and sulfonates such as methanesulfonates andtoluenesulfonates. Protective groups of this type are described byTheodora W. Green, Protective Groups in Organic Synthesis, John Wiley &Sons, 1981. However, the acetoxy group is particularly preferred.

This mono- or disubstituted hydroxyacetophenone is then esterified underconditions as stated before. The most preferred reagent is aceticanhydride. In this process, the 3,5-dibromo-4-hydroxyacetophenone isrefluxed with an excess of acetic anhydride for from about 15 to about20 hours. Excess acetic anhydride as well as generated acetic acid areremoved by distillation in vacuo. This is conducted, for example at apressure of from about 0.1 to about 760 mm Hg and at a temperature offrom about 15° C. to about 40° C., preferably from about 30° C. to about35° C.

The resultant3,5-dibromo-4-acetoxyacetophenone is then preferablyrecrystallized from an appropriate recrystallization solvent, preferablyan alcohol, and most preferably isopropanol. The3,5-dibromo-4-acetoxyacetophenone is then reduced with a suitablereducing agent to form 1-(3',5'-dibromo- 4'-acetoxyphenyl)ethanol. Onepreferred reducing agent is NaBH₄. Other reducing agents non-exclusivelyinclude lithium aluminum hydride, hydrogen, and diisobutyl aluminumhydride. The subsequent reduction of the ketone function can also bedone with other complex hydrides and by catalytic reduction withhydrogen. Lithium borohydride is also possible as well as reactionproducts that arise for example upon dissolution of sodium borohydrideor lithium borohydride in alcohols. The preferred reaction medium inreduction with complex hydrides is ethanol or mixtures of organicsolvents miscible with water, such as THF/water mixtures. The mostpreferred solvent is ethanol. This product is then dehydrated.Dehydration is preferably conducted by vacuum heating in the presence ofa polymerization inhibitor and a dehydrating agent. In one preferredembodiment, the 1-(3',5'-dibromo-4'-acetoxyphenyl)ethanol is mixed witha KHSO₄ dehydrating agent and t-butyl catechol as a polymerizationinhibitor. Other useful dehydrating agents non-exclusively includebases, CuSO₄, CuCl₂ and Al₂ O₃. Other polymerization inhibitorsnon-exclusively include hydroquinone, tetrachloroquinone anddi-t-butyl-p-cresol. The dehydrating agent is present in an amount offrom about 0.25 to about 5.0 percent weight of the ethanol. Thepolymerization inhibitor is preferably present in an amount of fromabout 0.01% to about 5% based on the weight of the ethanol. The reactionvessel is heated to from about 160° C. to about 210° C., preferably 168°C. to about 190° C. at a pressure of from about 0.01 to about 0.1 mm Hg.The resultant product is 3,5-dibromo-4-acetoxystyrene. The3,5-dibromo-4-acetoxystyrene monomer is then polymerized by a freeradical initiation process to produce poly(3,5 dibromo-4-acetoxystyrene)such that it has a molecular weight in the range of from about 1,000 toabout 800,000, preferably 5,000 to 500,000 or more, preferably about5,000 to about 300,000. This intermediate is then hydrolyzed with a baseor acid to form poly(3,5-dibromo-4-hydroxystyrene) such that it also hasthe molecular weight range of from about 1,000 to about 500,000,preferably about 5,000 to about 500,000.

One preferred free radical initiator is azoisobutyronitrile. Other azotype initiators are also suitable. Still others non-exclusively includeperoxides such as benzoyl peroxide, and di-t-butyl peroxide. It ispredicted that essentially any free radical initiation system will servein the same fashion. One preferred hydrolyzing agent is tetramethylammonium hydroxide. Other hydrolyzing agents non-exclusively includeaqueous NH₃, NaOH, KOH, HCl, and H₂ SO₄.

The following non-limiting examples serve to illustrate the invention.

EXAMPLE 1 3,5-Dibromo-4-hydroxyacetophenone

4-Hydroxyacetophenone (110.8 g, 0.81 mol) is dissolved in 50% aceticacid (1200 ml) and cooled in an ice bath. A solution of bromine (281.6g, 1.76 mol) in 80% acetic acid is added dropwise to the4-hydroxyacetophenone solution over a period of four hours. The reactiontemperature is maintained below 25° C. After the bromine addition iscomplete, a white solid precipitates. The solid is collected viafiltration and washed with water. Recrystallization with isopropylalcohol affords a white to light pink crystalline solid. The crystalsare dried in a vacuum oven at room temperature to afford 178.5 g of3,5-dibromo-4-hydroxyacetophenone.

3,5-Dibromo-4-acetoxyacetophenone

3,5-Dibromo-4-hydroxyacetophenone (154.0 g, 0.523 mol), acetic anhydride(100.0 ml) and sodium acetate (1.0 g) are placed in a one liter flaskand heated to reflux overnight. Unreacted acetic anhydride and aceticacid are removed via distillation at 0.1-0.25 mm Hg. A solid material isleft in the flask.

Recrystallization with isopropyl alcohol (110 ml) affords a light yellowcrystalline solid. The crystals are dried in a vacuum oven to yield161.8 g of 3,5-dibromo-4-acetoxyacetophenone.

1-(3',5'-Dibromo-4'-acetoxyphenyl)ethanol

3,5-Dibromo-4-acetoxyacetophenone (35.2 g, 0.1 mol) is suspended inabsolute alcohol (100 ml). The flask is cooled in ice and sodiumborohydride (1.9 g, 0.05 mol) is added slowly to the cooled reactionmixture. The reaction mixture is stirred at 0° C. for two hours. Water(300 ml) is added and the product is extracted with ethyl acetate (300ml). The organic layer is separated, dried over magnesium sulfate andconcentrated on the rotary evaporator to yield 30.7 g of1-(3',5'-dibromo-4'-acetoxyphenyl)ethanol.

3,5-Dibromo-4-acetoxystyrene

1 -(3',5'-Dibromo-4'-acetoxyphenyl)ethanol (104.86 g, 0.296 mol) KHSO₄(1.0 g) and t-butyl catechol (3.34 g) are mixed in a flask. The flask isequipped with a fractional distillation apparatus and attached to avacuum pump. Dehydration is conducted at 168°-187° C. under vacuum(0.05-0.10 mm Hg). The product is distilled at 116°-134° C. to yield anoily solid (61.82 g). Recrystallization from hexane gives whitecrystals, m.p. 76° C.

EXAMPLE 2 Polymerization

5 g of 3,5-dibromo-4-acetoxystyrene is combined with 25 ml of degassedtetrahydrofuran and 0.2g of azoisobutyronitrile as the free radicalinitiator. The reaction is conducted for 15 hours at 70° C. undernitrogen. The polymer is isolated by precipitation into water andfiltering to yield a poly(3,5-dibromo- 4-acetoxystyrene) having anaverage molecular weight of 3,700.

EXAMPLE 3 Hydrolysis

The reaction product of example 2 is hydrolyzed by mixing with 1 mltetramethyl ammonium hydroxide, and 10 ml methanol. The mixture isheated to 70° C. for 15 hours under nitrogen. The polymer is isolated byprecipitating into water and filtering to yieldpoly(3,5-dibromo-4-hydroxystyrene).

EXAMPLE 4 3,5-Dibromo-4-hydroxyacetophenone

A solution of 320 g or 103 ml (2 moles) bromine in 50 ml acetic acid isadded dropwise to a suspension of 136 g (1 mole) 4-hydroxyacetophenoneand 164 g (2 moles) sodium acetate in such a way that the temperaturedoes not rise above 30° C. After the bromine solution has beencompletely added, the reaction mixture is stirred for a further 20minutes following which it is poured into 2 liters of ice water andfinally the solid product is removed by filtration. The product isrinsed with water and recrystallized after drying from toluene or ethylacetate. A yield of 91% may be achieved. The vacuum-dried crystals havea melting point of 180°-184° C.

EXAMPLE 5 3,5-Dibromo-4-acetoxyacetophenone

15.7 g (0.2 mole) acetylchloride is added dropwise to a stirred mixtureof 57.1 g (0.194 mole) 3,5-dibromo-4-hydroxyacetophenone, 1.67 g4-dimethylaminopyridine, and 19.6 g triethylamine in toluene at 601/2°C. After four hours of further reaction under the given conditions, thehydrochloride precipitated from the solution is filtered off and thetoluene solvent is distilled from the remaining solution under vacuumand the remaining product is recrystallized from a mixture ofdiisopropyl ether and activated charcoal. A yield of 93% may beachieved. The white, isolated crystals have a melting point of 114° C.

EXAMPLE 6 1-(3',5'-Dibromo-4'-acetoxyphenyl)ethanol

5 g of sodium borohydride is added in small portions to an ice-cooledsolution of 84 g (0.25 mole) 3,5-dibromo-4-acetoxyacetophenone intetrahydrofuran and water. The reaction is exothermic. When all thesodium borohydride has been added and after a further 30 minutes ofstirring, the reaction mixture is nearly clear. The solution is broughtto a pH of 2 with 2 g hydrochloric acid, the solution is extracted twicewith ether, and the combined organic phases are rinsed twice with water.After drying the ether solution, the solution is concentrated undervacuum. A yellow oil is produced, which in a high vacuum has a boilingpoint of 132°-139° C. at 0.002 Torr (mbar). The yield of this reactionstage after distillation is 80 g of a colorless oil.

EXAMPLE 7 3,5-Dibromo-4-acetoxystyrene

A mixture of 67.6 g (0.02 mole)1-(3',5'-dibromo-4'-acetoxyphenyl)ethanol, 0.35 g freshly melted andthen finely pulverized potassium hydrogen sulfate, and 0.5 gt-butylhydroquinone are heated at 20 Torr to 170°-190° C. The resultingproduct is distilled off (under vacuum) at a temperature of 140° to 160°C. It is taken up in ether, the ether solution is washed with Na₂ CO₃,dried, and concentrated under vacuum. The remaining product is distilledat 0.02 mbar; the boiling point is 116° C. The isolated product, whichis a highly viscous oil or a white, waxy solid, has a melting point ofapproximately 75° C. The reaction yield is 27 g.

EXAMPLE 8 Preparation of 3,5-Dibromo-4-hydroxystyrene

10 g of 4-acetoxy-3,5-dibromostyrene are dissolved in 50 ml THF and 25ml methanol, 12 g hydrazine hydrate (80% aqueous solution) is added, andthe cloudy mixture is then converted into a clear solution by adding 3ml of water. After 40 minutes it is acidified with a semi-concentratedHCl to pH 2 and extracted twice with ether, the ether phase is washedtwice with water and dried over sodium sulfate, and the ether is removedwith a rotary evaporator at room temperature under aspirator vacuum. 8.5g of crude product remain, from which 6.45 g of white crystals (mp 74°C.) are obtained by recrystallization from petroleum ether.

EXAMPLE 9 o-Cresyl Acetate

First 235.5 g (3.3 moles) acetyl chloride then 282.8 g (2.8 moles)triethylamine are added dropwise to a mixture of 324 g (3 moles)o-cresol and 36.6 g (0.3 mole) 4-dimethylaminopyridine in 1 liter oftoluene. The mixture is then heated for 3 h at 65° C. The resultingsolid hydrochloride is separated by filtration and the organic phase iswashed twice with 1 N hydrochloric acid then with water. The solution isdried and then the solvent is recovered under vacuum. The remaining oilis distilled under vacuum. It has a boiling point of 87° C. at 12 Torr.The yield is 428.8 g.

EXAMPLE 10 4-Hydroxy-5-methylacetophenone

A total of 360 g dry AlC13 is added to a mixture of 300 g (2 moles)o-cresyl acetate and 1.2 liters nitrobenzene in small portions. Thereddish mixture is kept at room temperature with moisture excluded for12 h, and the mixture increasingly takes on a dark-green color. When thereaction mixture is poured into ice water, a light yellow emulsion isobtained, to which the quantity of a 10% hydrochloric acid needed tomake it clear is added. After 1 liter of ether has been added, twophases form, from which the ether phase is separated and washed with a7.5% potassium hydroxide solution. The aqueous phase is combined withthe potassium hydroxide solution, acidified, and the resulting product,after extraction with ether, drying, and recrystallization fromdiisopropyl ether, is isolated. The light-brown product has a meltingpoint of 108° to 109° C. The reaction yield is 122.8 g.

EXAMPLE 11 3-Bromo-4-hydroxy-5-methylacetophenone

110 g (0.73 mole) 4-hydroxy-5-methylacetophenone is suspended in amixture of 370 ml acetic acid (glacial) and 370 ml H₂ O, the mixture iscooled to 5° C., and a solution of 116.8 g or 38 ml (0.73 mole) brominein 100 ml acetic acid is added dropwise while cooling such that thetemperature does not rise above 10° C. Addition of bromine takes about 1h. After cooling for a further 2 h at room temperature, the product isfiltered off, dried, and recrystallized from acetonitrile. 150 g ofproduct with a melting point of 145°-146° C. can be isolated.

EXAMPLE 12 3-Bromo-4-acetoxy-5-methylacetophenone

52 g or 47 ml (0.66 mole) acetyl chloride are added dropwise to asolution of 140 g (0.6 mole) 3-bromo-4-hydroxy-5-methylacetophenone, 7.4g 4-dimethylaminopyridine and 60.6 g (0.6 mole) triethylamine in 500 mltoluene. The resulting reaction mixture is stirred for another 3 h at65° C. The hydrochloride formed is filtered off and the toluene phase iswashed twice with 2 N hydrochloric acid then twice with water. Afterdrying and distillation of the solvent under vacuum, 99 g of pureproduct is isolated. The white crystals have a melting point of 78°-80°C.

EXAMPLE 13 1-(3'-Bromo-4'-acetoxy-5'-methylphenyl)ethanol

99 g (0.37 mole) of 3-bromo-4-acetoxy-5-methylacetophenone is added to250 ml of tetrahydrofuran and cooled to 0° C. 20 ml water is added andthen 7 g (0.185 mole) sodium borohydride is added while cooling inportions such that the temperature does not exceed 20° C. After twohours stirring at room temperature, the reaction mixture is added to amixture consisting of 100 ml concentrated hydrochloric acid, 200 mlwater, and 250 g ice, the mixture is thoroughly stirred, and thenextracted with ether. The ether phase is washed first with a 5% sodiumcarbonate solution then with water. After distilling the solvent, 96.3 gof a viscous oil is obtained as the crude product, and this is thendistilled under vacuum according to H₃ and yields 86.8 g of product.

EXAMPLE 14 3-Bromo-4-acetoxy-5-methylstyrene

A mixture of 28 g 1-(3'-bromo-4'-acetoxy-5'-methylphenyl)ethanol and 0.5g freshly prepared potassium hydrogen sulfate is heated under a 20 Torrvacuum to 190°-200° C. The distillate is transferred to an ice-filledreaction vessel which contains 2 g t-butylhydroquinone. After 2 h, thedistillate is taken up in ether, the ether phases are treated with a 5%sodium carbonate solution and dried, then the solvent is distilled offunder vacuum. At 0.05 Torr, 6.8 g of an impure product is obtained at atemperature of 86 to 89° C., from which 18 g of pure monomer can beobtained.

EXAMPLE 15 Attempted direct reduction of3,5-dibromo-4-hydroxyacetophenone

10 g of 3,5-dibromo-4-hydroxyacetophenone are dissolved in methanol,cooled to 0° C., at which point the calculated amount of sodium boronhydride is slowly added with stirring. After one minute, thin layerchromatography shows the presence of 4-ethylphenol, but not of1-(3',5'-dibromo-4,-hydroxyphenyl)ethanol (by comparison with authenticsamples). After one hour, the mixture is worked up by pouring intowater, extracting the ether, and drying on a rotary evaporator. Analysisof the products by NMR spectroscopy shows the material to be a mixtureof starting material and 4-ethylphenol, with no alcohol reductionproduct present.

Similar results are obtained with other solvents and complex hydrides aswell as with attempted catalytic hydrogenations.

EXAMPLE 16 Dehydration of 1-(3',5'-dibromo-4'-acetoxyphenyl)ethanol withcopper (II) sulfate

5 g 1-(3',5'-dibromo-4-acetoxyphenyl)ethanol are dissolved in 50 g oftoluene, to which mixture are added 0.25 g of anhydrouscopper(II)sulfate. The mixture is refluxed for 2 hours and the toluenethen removed on a rotary evaporator. A yellow oil remains which afterrecrystallization from petrol ether yields 2.9 g of3,5-dibromo-4-hydroxystyrene as white crystals, mp. 75° C.

What is claimed is:
 1. A method for preparing 3-mono- and3,5-dihalogenated 4-hydroxy and 4-acetoxystyrenes which comprises(a)halogenating a 4-hydroxyacetophenone with general formula ##STR5##wherein R₁ is hydrogen or C₁ to C₁₀ alkyl; and R₂ and R₃ areindependently hydrogen, alkyl, alkoxy, or halogen, wherein R₁ and R₂ maybe combined to form a cycloaliphatic ring, consisting of 6 to 12members, (b) esterification of the hydroxyl function to form ahalogenated 4-acetoxyacetophenone derivative, (c) reduction of theketone function to a hydroxyl function, (d) dehydration to form 3-monoor 3,5-dihalogenated 4-acetoxystyrene; with optional (e) hydrolysis toform the 3-mono or 3,5-dihalogenated 4-hydroxystyrene.
 2. A methodaccording to claim 1 whereinR₁ is hydrogen or (C₁ -C₃) alkyl, and R₂ andR₃ are the same and are hydrogen, C₁ -C₃ alkyl, C₁ -C₃ alkoxy, orbromine.
 3. A method according to claim 1 wherein step (b) is carriedout with a halogen.
 4. A method according to claim 1 wherein step (c),esterification, is carried out with acetyl chloride or acetic anhydride.5. A method according to claim 1 wherein reduction is carried out eithercatalytically with hydrogen or with complex hydrides.
 6. A methodaccording to claim 1 wherein dehydration is carried out by heating undervacuum in the presence of a polymerization inhibitor and a dehydratingagent.
 7. A method according to claim 1 wherein hydrolysis is carriedout in an alkali or an acid.